Week_8_Answers - STUDY QUESTIONS (Lectures 26-28) 1)...

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STUDY QUESTIONS (Lectures 26-28) 1) Briefly describe the experiment at Cedar Creek research station, the results discovered, and name two hypothetical processes that could account for the results. Tilman and colleagues set up a series of plots in the tallgrass prairie in central Minnesota. In these plots, the diversity of species planted was varied (but the number was kept constant). The productivity of each plot was measured over several years. These researchers found that productivity increased with species diversity (especially in the later years of the study). Some hypothetical processes that could account for this pattern: 1) Resource partitioning (different species may be able to use different nutrients, such as N, in different ways) 2) Disease susceptibility (monocultures may be more susceptible to specialist pathogens than highly diverse plots) 3) Facilitation (certain species may facilitate the growth of other species, such as nitrogen fixation in legumes providing usable nitrogen for other species) 4) Sampling effect (some species may simply be better growers and as plots get more diverse such “super” species are more likely to be included). 2) Farmers in central Minnesota can grow corn and/or soybeans. Corn is harvested in August, and soybeans are harvested in late June or early July. Additionally, soybeans are nitrogen fixers. Based on this information, give two reasons why you might advise farmers to intercrop (that is, grow corn and soybeans in alternate rows) to increase their yield (hint: see question 1). Some potential reasons include: 1. Facilitation : the soybeans may enrich the nitrogen concentration in the soil for the corn. 2. Disease susceptibility : a pathogen that specializes on corn or soybeans may not spread as quickly through an intercropped population as it will through a monoculture. 3)
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This note was uploaded on 04/20/2008 for the course BIOL 180 taught by Professor Freeman during the Winter '07 term at University of Washington.

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Week_8_Answers - STUDY QUESTIONS (Lectures 26-28) 1)...

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